As much as I despise ads, this is a pretty delusional take. Mastodon was only possible because of the hard work of open source contributors with day jobs that feed them. Running and accessing these instances requires all sorts of costly infrastructure that doesn’t materialise out of the blue. And finally, there may be a handful of geeks that enjoy paying for hosting, but that only works as long as it’s a niche community. Introduce 2 billion users, and it becomes just plain impossible.

And as you cite piracy as an alternative: that’s not "free" as in software, that’s "free" as in freeloading. Someone else is paying for it, just not you. That might work to fulfil your own needs, but it’s not a viable solution for business models.